How to Hide the "MoonClerk" Admin Menu

function plt_hide_moonclerk_wp_shortcode_menus() {
	//Hide the "Tools → MoonClerk" menu.
	remove_submenu_page('tools.php', 'moonclerk-wp-shortcode/moonclerk-wp-shortcode.php');
}

add_action('admin_menu', 'plt_hide_moonclerk_wp_shortcode_menus', 11);

Where do I put this code?